Cold cleaning is an application where numerous solvents are used. In most cold cleaning applications, the soiled part is either immersed in the fluid or wiped with rags or similar objects soaked in solvents and allowed to air dry.
In cold cleaning applications, the use of the aerosol packaging concept has long been found to be a convenient and cost effective means of dispensing solvents. Aerosol products utilize a propellant gas or mixture of propellant gases, preferably in a liquified gas rather than a compressed gas state, to generate sufficient pressure to expel the active ingredients, i.e. product concentrates such as solvents, from the container upon opening of the aerosol valve. The propellants may be in direct contact with the solvent, as in most conventional aerosol systems, or may be isolated from the solvent, as in barrier-type aerosol systems.
Vapor degreasing and solvent cleaning with fluorocarbon based solvents have found widespread use in industry for the degreasing and otherwise cleaning of solid surfaces, especially intricate parts and difficult to remove soils.
In its simplest form, vapor degreasing or solvent cleaning consists of exposing a room temperature object to be cleaned to the vapors of a boiling solvent. Vapors condensing on the object provide clean distilled solvent to wash away grease or other contamination. Final evaporation of solvent from the object leaves behind no residue as would be the case where the object is simply washed in liquid solvent.
For difficult to remove soils where elevated temperature is necessary to improve the cleaning action of the solvent, or for large volume assembly line operations where the cleaning of metal parts and assemblies must be done efficiently and quickly, the conventional operation of a vapor degreaser consists of immersing the part to be cleaned in a sump of boiling solvent which removes the bulk of the soil, thereafter immersing the part in a sump containing freshly distilled solvent near room temperature, and finally exposing the part to solvent vapors over the boiling sump which condense on the cleaned part. In addition, the part can also be sprayed with distilled solvent before final rinsing.
Vapor degreasers suitable in the above-described operations are well known in the art. For example, Sherliker et al. in U.S. Pat. No.3,085,918 disclose such suitable vapor degreasers comprising a boiling sump, a clean sump, a water separator, and other ancillary equipment.
Chlorofluorocarbon solvents, such as trichlorotrifluoroethane, have attained widespread use in recent years as effective, nontoxic, and nonflammable agents useful in degreasing applications and other solvent cleaning applications. One isomer of trichlorotrifluoroethane is 1,1,2-trichloro-1,2,2-trifluoroethane (known in the art as CFC-113). CFC-113 has a boiling point of about 47.degree. C. and has been found to have satisfactory solvent power for greases, oils, waxes and the like. It has therefore found widespread use for cleaning electric motors, compressors, heavy metal parts, delicate precision metal parts, printed circuit boards, gyroscopes, guidance systems, aerospace and missile hardware, aluminum parts and the like.
Another commonly used solvent is chloroform (known in the art as HCC-20) which has a boiling point of about 63.degree. C. Perchloroethylene is a commonly used dry cleaning and vapor degreasing solvent which has a boiling point of about 121.degree. C. These compounds are disadvantageous for use as solvents because they are toxic; also, chloroform causes liver damage when inhaled in excess.
Although chlorine is known to contribute to the solvency capability of a compound, fully halogenated chlorofluorocarbons and hydrochlorocarbons are suspected of causing environmental problems in connection with the earth's protective ozone layer. Thus, the art is seeking new compounds which do not contribute to environmental problems but yet provide the solvency properties of CFC-113. From an environmental standpoint, hydrofluorocarbon and hydrocarbon compounds are of interest because they are considered to be stratospherically safe substitutes for the currently used fully halogenated chlorofluorocarbons. Mathematical models have substantiated that hydrofluorocarbons and hydrocarbons will not adversely affect atmospheric chemistry as not contributing to ozone depletion and to green-house global warming in comparison to the fully halogenated species.
The problems with hydrofluorocarbons as solvents are that known straight chain hydrofluorocarbons such as CH.sub.3 (CF.sub.2).sub.4 H and CH.sub.3 CH.sub.2 (CF.sub.2).sub.3 H do not have the solvency power of CFC-113. A branched hydrofluorocarbon such as CF.sub.3 CH(CF.sub.3).sub.2 is nonflammable but has a boiling point of about 15.degree. C. and thus, is not liquid at room temperature at atmospheric pressure and is not useful in cold cleaning applications. The problems with hydrocarbons as solvents are that branched hydrocarbons such as isobutane are flammable and have such low boiling points that they are not liquid at room temperature and are not useful in cold cleaning applications. The problem with alkanols as solvents is that branched alkanols such as isobutanol are flammable.
It is an object of this invention to provide novel hydrofluorocarbon compounds which are liquid at room temperature and which are useful as solvents for use in vapor degreasing, cold cleaning, and other solvent cleaning applications including defluxing applications and dry cleaning.
Another object of the invention is to provide novel environmentally acceptable solvents for use in the aforementioned applications.
Other objects and advantages of the invention will become apparent from the following description.